Laboratory Control Sample (LCS) is a specimen of known composition prepared using contaminant-free reagent water, or an inert solid, that is spiked with the analyte of interest at the midpoint of the calibration curve or at the level of concern; and then analyzed using the same preparation, reagents, and analytical methods employed for regular specimens and at the intervals set in the QA Project Plan.

The Laboratory Data Qualifier is a Code applied to the data by the analytical testing facility to indicate a verifiable or potential data deficiency or bias.

Laboratory Duplicates are two or more representative portions taken from one homogeneous sample by the analyst and analyzed in the same testing facility.

Lactate means to secrete or produce milk.

Deutsch: Laktation / Français: Lactation / Italiano: Lattazione 

Lactation refers to the secretion of milk from the mammary glands, and the period of time that a mother lactates to feed its young. This process can occur with almost all post-partum female mammals, although it may have predated the existence of mammals. The process may also be referred to as breastfeeding or nursing when referring to humans.

A lacustrine zone is area of a reservoir which is most lake -like: current velocities are much slower than for riverine or transitional zones.

A Lagoon is Earthen storage structure with sufficient dilution water added to allow Microorganisms to biodegrade and treat

A lake is a standing body of water greater than 1 hectare (about 2.5 acre) that has at least 1000 m² (about 0.25 acre) of open water and is at least 1 meter (about

lakes are substantial inland bodies of standing water.

A Lambert's azimuthal map projection is the map projection used for laying out the EMAP grid.